In this Dec. 10, 1995 file photo, American professor F. Sherwood Rowland (l.) receives the Nobel prize for chemistry from Swedish King Carl XVI Gustaf at the Concert Hall in Stockholm, Sweden.

Eric Roxfelt/AP/File

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LOS ANGELES

F. Sherwood Rowland, the Nobel prize-winning chemist who sounded the alarm on the thinning of the Earth's ozone layer and crusaded against the use of man-made chemicals that were harming earth's atmospheric blanket, has died. He was 84.

"We have lost our finest friend and mentor," Kenneth C. Janda said in a statement. "He saved the world from a major catastrophe: never wavering in his commitment to science, truth and humanity and did so with integrity and grace."

Rowland was among three scientists awarded the 1995 Nobel Prize for chemistry for explaining how the ozone is formed and decomposed through chemical processes in the atmosphere.

The prize was awarded more than two decades after Rowland and his post-doctoral student Mario Molina calculated that if human use of chlorofluorocarbon, a byproduct of aerosol sprays, deodorants and other household products was to continue at an unaltered rate, the ozone layer would be depleted after several decades. Their work at UC Irvine built upon findings by atmospheric scientist Paul Crutzen.

Their prediction caught enormous attention and was strongly challenged partly because CFC's non-toxic properties were thought to be environmentally safe. Their work gained widespread recognition more than a decade later with the discovery of the ozone hole over Earth's polar regions and leaders of nations worldwide began to act to ban or curb usage of the chemicals.

"It was to turn out that they had even underestimated the risk," a Nobel committee said in its award citation for Rowland, Molina and Crutzen.

Molina said his former mentor never shied from defending his work or advocating a ban on CFC.

"He showed me that if we believe in the science ... we should speak out when we feel it's important for society to change," Molina told the Associated Press.

His work on ozone depletion made Rowland a prominent voice for scientists concerned about global warming.

"Isn't it a responsibility of scientists, if you believe that you have found something that can affect the environment, isn't it your responsibility to do something about it, enough so that action actually takes place?"Rowland said at a White House climate change roundtable in 1997.

"If not us, who? If not now, when?" he asked.

Rowland, who was known by those who knew him as "Sherry," was survived by his wife of nearly 60 years, Joan, a son and a daughter.